Effect of Particle Size on Droplet Infiltration into Hydrophobic Porous Media As a Model of Water Repellent Soil

Hamlett, Christopher; Shirtcliffe, Neil; McHale, Glen; Ahn, Sujung; Bryant, R.; Doerr, Stefan H.; Newton, Michael I.

doi:10.1021/es202319a

Cited by 26 publications

(25 citation statements)

References 19 publications

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“…The beads were immersed in HCl (30 vol.%) for 24 h and rinsed three times with distilled water and dried at 100 C for 12 h to achieve fully hydrophilic particles. A subsample of these was immersed in chlorotrimethylsilane (>97% Sigma-Aldrich, UK) solution (2 vol.% in toluene; >99.8% Fisher Scientific, UK) for 48 h and rinsed five times with toluene and then dried at room temperature to generate a hydrophobized sample set of particles (Hamlett et al, 2011).…”

Section: Methodsmentioning

confidence: 99%

“…This study aimed to address this research gap by investigating the splash behaviour from a single water drop impact on beds of hydrophobic and hydrophilic spherical glass beads (serving as simple water repellent and wettable model soils respectively) under controlled laboratory conditions. Hydrophilic and hydrophobic glass particles have previously been used to provide a simple 'model' analogue for soil for particulate wettability studies (Hamlett et al, 2011). This use of 'model' soil analogues allows elimination of the aforementioned water film effect, while keeping all other variables other than water repellency constant.…”

Section: Introductionmentioning

confidence: 99%

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Effects of hydrophobicity on splash erosion of model soil particles by a single water drop impact

Ahn

Doerr

Douglas

et al. 2013

Earth Surf Processes Landf

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Northumbria University has developed Northumbria Research Link (NRL) to enable users to access the University's research output. Copyright © and moral rights for items on NRL are retained by the individual author(s) and/or other copyright owners. Single copies of full items can be reproduced, displayed or performed, and given to third parties in any format or medium for personal research or study, educational, or not-for-profit purposes without prior permission or charge, provided the authors, title and full bibliographic details are given, as well as a hyperlink and/or URL to the original metadata page. The content must not be changed in any way. Full items must not be sold commercially in any format or medium without formal permission of the copyright holder. The full policy is available online: http://nrl.northumbria.ac.uk/policies.html This document may differ from the final, published version of the research and has been made available online in accordance with publisher policies. To read and/or cite from the published version of the research, please visit the publisher's website (a subscription may be required.) ABSTRACTRaindrop impact can be a major contributor to particle mobilization for soils and other granular materials. In previous work, water repellent soils, comprised of hydrophobic particles, have been shown to exhibit greater splash erosion losses under multiple drop impact. However, the underlying principal differences in splash behavior between hydrophobic and hydrophilic granular surfaces have not been studied to date. In this study the effects of particle hydrophobicity on splash behaviour by a single water drop impact were examined using high-speed videography. Water drops (4 mm in diameter) were dropped on beds of hydrophilic and hydrophobic glass beads (sieved range: 350400 m), serving as model soil particles. The drop velocity on impact was 2.67 m s -1 , which corresponds to 30% of the terminal velocity of a raindrop of similar size. The resulting impact behaviour was measured in terms of the trajectories of particles ejected from the beds and their final resting positions. The response to the impacting water drop was significantly different between hydrophilic and hydrophobic particles in terms of the distance distribution, the median distance travelled by the particles and number of ejected particles. The greater ejection distances of hydrophobic particles were mainly the result of the higher initial velocities rather than differences in ejecting angles. The higher and longer 2 ejection trajectories for hydrophobic particles, compared to hydrophilic particles, indicate that particle hydrophobicity affects splash erosion from the initial stage of rainfall erosion before a water layer may be formed by accumulating drops. The ~10% increase in average splash distance for hydrophobic particles compared to hydrophilic particles suggests that particle hydrophobicity can result in greater net erosion rate, which would be amplified on sloping surfaces, for example, by ridges in ploughed agri...

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effects of hydrophobicity on splash erosion of model soil particles by a single water drop impact

Ahn

Doerr

Douglas

et al. 2013

Earth Surf Processes Landf

Self Cite

View full text Add to dashboard Cite

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“…Contact angle, being the quantitative measurement of wettability, is therefore influenced by many environmental and physicochemical factors such as relative humidity, temperature, presence of organic matter, roughness and heterogeneity of the surfaces, shape and size of the particles, liquid properties, drop size, etc. (Dekker et al 1998;De Jonge et al 1999;Lam et al 2001;Doerr et al 2005;Hamlett et al 2011;Leelamanie and Karube 2012). In spite of the fact that determining contact angles is challenging as there are too many factors affecting the measurements, the contact angle is of practical importance in understanding the hydrologic functions of unsaturated soils during natural wetting and drying processes.…”

Section: Introductionmentioning

confidence: 99%

Soil-water contact angle as affected by the aqueous electrolyte concentration

Leelamanie

Karube

2013

Soil Science and Plant Nutrition

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Electrolyte concentration changes the surface tension of the water-air interface, which is expected to affect the solid-water contact angle. In the present study, we focused on examining the effects of aqueous electrolyte concentration on the contact angle of soil samples with different hydrophobicities using sodium chloride (NaCl) and calcium chloride (CaCl 2 ) solutions. Japanese Andisol and silica sand were hydrophobized using stearic acid to obtain different hydrophobicities. The contact angle of all the samples increased with increasing electrolyte concentration. This was attributed to the increasing surface tension of the solutions. The response of contact angle to the electrolyte concentration was positively correlated with soil surface free energy fitting into a linear relationship in Andisol, but not in silica sand. Surface tension of electrolyte solutions increases linearly with electrolyte concentration up to high salinities, and the contact angle can be expected to increase with increasing electrolyte concentration in a corresponding pattern. The relationship observed in the present study was non-linear, where more prominent increase of contact angle was observed at low electrolyte concentrations. The response of contact angle to the increasing electrolyte concentration was almost negligible at concentrations higher than 0.06 mol L ) for CaCl 2 solutions. The lowered solid-liquid interfacial free energy and its effects on contact angle with increasing adsorption of ions at the interface was considered to be the reason for decreasing slopes of the curves. Initial increase in contact angle with increasing ionic strength of CaCl 2 was lower than that of NaCl. This might be because the adsorption of ions on soil surfaces, and the consequent effects on lowering the free energy of the solid-liquid interface and the contact angle, are more pronounced for calcium ions (Ca 2+ ) than for sodium ions (Na + ).

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“…According to Young–Laplace equation (Fisher, 1926), a contact angle of 90° marks the theoretical threshold for attraction or repulsion between two particles or infiltration to occur or not in granular media. This is disputed and shown to be as low as 55° (Hamlett et al, 2011). This study focus on wettability conditions 0 to 90°, where water retention occurs but is likely to be influenced by the contact angles.…”

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confidence: 99%

Hysteresis in the Soil Water Retention of a Sand–Clay Mixture with Contact Angles Lower than Ninety Degrees

Lourenço

Jones

Morley

et al. 2015

Vadose Zone Journal

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Soil water retention curves (SWRCs) are usually obtained on the assumption small water menisci spread in the surface of particles yielding contact angles near zero degrees. While this is true at high water contents, where pores are filled by water or a film of water covers the particles, it is less likely for drier states, where the adhesion of water menisci to the surface of the particles is controlled by the nature of the particle surface (chemistry and surface roughness) and the presence of organic matter. Here, we investigate hysteretic effects in the relation between water content and soil particle wettability versus suction for model samples following drying and wetting paths. A comparison is done for a model material (mixture of sand and clay) with and without water repellent substances, being the samples with water repellent substances in a subcritical water repellent state (contact angles <90°). Wettability was manipulated by treatment with organic acids that mimic the chemistry of natural water repellent substances. Suction was measured directly with a high suction tensiometer and wettability via contact angles by the sessile drop method. The results revealed lower water retention and greater contact angles for the subcritical water repellent samples, following both drying and wetting paths. Hysteresis was present in the relation between the contact angles and suction for the subcritical water repellent samples.Abbreviations: SWRCs, soil water retention curves. Soil water retention curves or capillary pressure-saturation relations are a relation between soil water content and suction as soils dry or wet. The boundaries are the main drying and main wetting curves, which are enclosed by ascending or descending scanning curves (Tompsett et al., 2005). Soil water retention curves are usually obtained on the assumption that soils small water menisci spread in the surface of particles yielding contact angles near 0°. While this is true at high water contents, where water fills the pores or a film of water covers the particles, it is less likely for drier states, where the adhesion of water menisci to the surface of the particles is controlled by the nature of the particle surface (chemistry and surface roughness) and the presence of organic matter. According to Young-Laplace equation (Fisher, 1926), a contact angle of 90° marks the theoretical threshold for attraction or repulsion between two particles or infiltration to occur or not in granular media. This is disputed and shown to be as low as 55° (Hamlett et al., 2011). This study focus on wettability conditions 0 to 90°, where water retention occurs but is likely to be influenced by the contact angles. Czachor et al. (2010) obtained the SWRCs for sands prepared at different wettability levels within the 0 to 90° range and up to suctions of 4 kPa by the hanging-column method. The results revealed differences between the drying and wetting paths. Liu et al. (2012) obtained the SWRC at low suctions with the hanging column method and the pressure plate up to t...

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Effect of Particle Size on Droplet Infiltration into Hydrophobic Porous Media As a Model of Water Repellent Soil

Cited by 26 publications

References 19 publications

Effects of hydrophobicity on splash erosion of model soil particles by a single water drop impact

Effects of hydrophobicity on splash erosion of model soil particles by a single water drop impact

Soil-water contact angle as affected by the aqueous electrolyte concentration

Hysteresis in the Soil Water Retention of a Sand–Clay Mixture with Contact Angles Lower than Ninety Degrees

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